Nanosecond Laser Pulses Research Articles

Room-temperature ferromagnetic MnGa nanoparticles in dilute magnetic semiconductor (Ga, Mn)As thin film: preparation and characterization.

The diluted magnetic semiconductor, (Ga, Mn) As, with the unique advantage of manipulating the spin and charge was widely investigated in the scientific community and considered as a potential material for the spintronic devices. However, its Curie temperature (Tc), which is limited to around 200 K, hinders the research progress of diluted magnetic semiconductors for potential device applications. Herein, we propose an approach to prepare the MnGa nanoparticles embedded in (Ga, Mn)As matrix using the magnetron sputtering deposition of Mn on GaAs surface, followed by the nano-second pulsed laser annealing, which gives a Tc above 400 K. We demonstrate that the MnGa nanoparticles are only formed in (Ga, Mn)As during the nano-second pulsed laser annealing under a critical range of energy density (0.4-0.5 J/cm2). This method for preparing the hybrid system of ferromagnetic metal/dilute magnetic semiconductor builds a platform for exploring the interesting spin transport phenomenon and is promising for the application of spintronic devices.&#xD.

Optical absorption studies of pulsed-laser-engineered silver nanospheres and their enhanced catalytic performance in the degradation of toxic methylene blue dye

Pulsed laser ablation in liquid is an environment-friendly and one of the fastest physical routes to synthesize surfactant-free and stable metal/metal oxide nanoparticles with high purity and no harmful residues. In this study, we report the synthesis of silver nanospheres (AgNSs) using the nanosecond pulsed laser ablation in liquid (PLAL) technique resulting in the formation of a colloidal solution. Investigation of the optical properties using UV–Vis spectroscopy revealed the effects of laser wavelength, frequency, fluence, ablation time, and re-irradiation on the light absorption of the produced silver nanospheres. Physicochemical characterizations included FE-SEM, XRD, DLS, FTIR, and XPS techniques to evaluate the size, morphology, crystal structure, size distribution, zeta potential, and surface chemistry. FE-SEM studies revealed the formation of well-dispersed spherical Ag nanospheres with an average particle size of 209 nm without any agglomeration. DLS measurements showed high stability with a recorded zeta potential value of −38.27 (+/−1.81) mV and a wider size distribution. The XRD analysis indicated a face-centered cubic crystal structure with the formation of an oxide layer over the metallic silver core. The presence of silver and oxygen was confirmed through XPS studies with binding energies at 368.1 eV and 374.1 eV and oxide formation on the surface of Ag NSs. Finally, the catalytic activity of the Ag colloid was examined for the degradation of the toxic methylene blue dye. The results revealed an excellent catalytic response with 90 % of the dye degraded in just 15 min of reaction time. The kinetics of the degradation process were studied with a rate constant of 0.054/min−1 showcasing the effectiveness of the pulsed laser-synthesized silver colloidal nanomaterial as a sustainable approach for environmental remediation.

Eco‐efficient recycling of carbon fibers from CFRP waste: A two‐step strategy by nanosecond pulsed laser

Eco‐efficient recycling of carbon fibers from <scp>CFRP</scp> waste: A two‐step strategy by nanosecond pulsed laser

Design of a compact beam transport system for laser-driven proton therapy

Abstract We put forward a new design of a compact beam transport system for intense laser-driven proton therapy, where instead of using conventional pulsed solenoids, our design relies on a helical coil irradiated by a nanosecond laser pulse to generate strong magnetic fields for focusing protons. A pair of dipole magnets and apertures are employed to further filter protons with large divergences and low energies. Our numerical studies combine particle-in-cell simulations for laser-plasma interaction to generate high-energy monoenergetic proton beams, finite element analysis for evaluating the magnetic field distribution inside the coil, and Monte-Carlo simulations for beam transport and energy deposition. Our results show that with this design, a spread-out Bragg peak in a range of several centimeters to a deep-seated tumor with a dose of approximately 16.5 cGy and fluctuation around 2% can be achieved. The instantaneous dose rate reaches up to 109 Gy/s, holding the potential for future FLASH radiotherapy research.

Optical and sign-flipping nonlinear optical properties of NiO/PMMA/PANI nanocomposite films

In this study, we introduce an efficient nanocomposite system to enhance optical properties of Nickel oxide (NiO) integrated with two polymers matrix. NiO nanoparticles is prepared using chemical co-precipitation method and its nanocomposite films (NCFs) were prepared with poly methyl methacrylate (PMMA) and polyaniline (PANI) using drop-casting method on glass substrate and was optimized by changing the concentration of NiO. The prepared NCFs were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), ultraviolet (UV)-visible absorption spectroscopy, photoluminescence (PL) spectroscopy and X-ray photoelectron (XPS) spectroscopy. The open-aperture z-scan method is employed for nonlinear optical investigations, utilizing a nanosecond pulsed laser with a wavelength of 532 nm for excitation. The findings indicate that the NCFs exhibit sign-flipping nonlinear behavior, indicating a transition from saturable absorption to reverse saturable absorption. This suggests that our NCFs exhibit optical limiting properties and potential for applications in photonic devices, such as optical switches and laser protection systems.

High-pulse-energy ultrafast 3 µm laser generation through OPG/DFG in PPMgLN

Abstract We report high-pulse-energy ultrafast 3 µm laser generation through optical parametric generation/difference frequency generation (OPG/DFG) in periodically poled magnesium-oxide-doped lithium niobate (PPMgLN). A commercial 1030 nm femtosecond laser is applied as the pump light and a homemade broadband nanosecond pulse laser around 1580 nm is used as the signal light in DFG. The broadband 1580 nm laser has a master oscillator power amplifier (MOPA) structure with a directly modulated superluminescent light-emitting diode (SLED) as the pulse seed and three stages of Er/Yb fiber amplifiers to lift its average power. A portion of the 1030 nm output pulse is converted to an electronic pulse via a pin detector, which is used as the trigger signal of the SLED driving circuit to ensure synchronization between the signal and the 1030 nm pump pulse. When injecting 2.12 W pump light into the PPMgLN, a broadband mid-infrared (MIR) output of 280 mW can be achieved directly through OPG with a center wavelength around 2.94 μm, a pulse width of 1.38 ps and a pulse repetition frequency of 500 kHz. The corresponding MIR pulse energy is 0.56 µJ. When injecting 2.62 W signal light simultaneously, a MIR output of 300 mW is achieved through the DFG process at the same pulse repetition frequency, corresponding to a pulse energy of 0.6 µJ. The conversion efficiency of the ultrafast pump laser to MIR reaches 14.1%. This high-pulse-energy 3 μm ultrafast laser has great prospects for applications in biological tissue ablation.

Design of Nanosecond Pulse Laser Diode Array Driver Circuit for LiDAR

The pulse laser emission circuit plays a crucial role as the emission unit of time-of-flight (TOF) LiDAR. This paper proposes a nanosecond-level pulse laser diode array drive circuit for LiDAR, primarily aimed at addressing the issue of high-speed scanning drive for the laser diode array at the emission end of solid-state LiDAR. Based on the single pulse laser diode drive circuit, this paper innovatively designs a circuit that includes modules such as a boost circuit, linear power supply, high-speed gate driver, GaN field-effect transistor, and pulse narrowing circuit, realizing an 8-channel laser diode array drive circuit. This circuit can achieve a pulse laser array drive with a single channel operating frequency of greater than 100 kHz, an output pulse width of less than 5 ns, a peak power greater than 75 W, and a channel switching time that does not exceed 1 μs. A field programmable gate array (FPGA) is used to control the operation of this circuit and perform a series of performance tests. Experimental results show that this circuit has a high repetition rate, large output power, a narrow pulse width, and fast switching speeds, making it highly suitable for use in the optical emission module of solid-state LiDAR.

Chaos-driven detection of methylene blue in wastewater using fractional calculus and laser systems

Abstract Methylene blue (MB) concentrations in residual water were detected using fractional calculus, the Rössler chaotic attractor and laser systems. A Nd:YVO4 nanosecond pulsed laser at 532 nm, with pulse energies ranging from 2 µJ to 7 µJ, was applied to irradiate different water samples containing MB concentrations from 20 µl to 100 µl. Fractional calculus was employed with the purpose of modeling the temperature distribution in the samples, with the Caputo fractional derivative describing photothermal effects induced by laser irradiation. Different MB concentrations were detected by using the Rössler chaotic attractor, it monitored variation on concentrations, associating attractor shapes with MB concentrations. Lower concentrations showed a weaker attractor response, whereas higher concentrations manifest stronger attractor shapes in magnitude. Raman spectroscopy confirmed the detection of MB in residual water from the Requena dam, located in Tepeji del Río de Ocampo, Hidalgo, Mexico. The application of fractional calculus improved the prediction of heat distribution in the samples, by incorporating numerical simulation. The results suggest that this approach is suitable for real-time monitoring, as it associates MB concentrations with distinct chaotic attractor shapes. This technique shows promise for the detection of other contaminants as well. Future research should focus on refining this method and expanding its application to develop innovative monitoring solutions.

An Investigation of Oxides of Tantalum Produced by Pulsed Laser Ablation and Continuous Wave Laser Heating.

Recent progress has seen multiple Ta2O5 polymorphs generated by different synthesis techniques. However, discrepancies arise when these polymorphs are produced in widely varying thermodynamic conditions and characterized using different techniques. This work aimed to characterize and compare Ta2O5 particles formed at high and low temperatures using nanosecond pulsed laser ablation (PLA) and continuous wave (CW) laser heating of a local area of tantalum in either air or an 18O2 atmosphere. Scanning electron microscopy (SEM) and Raman spectroscopy of the micrometer-sized particles generated by PLA were consistent with either a localized amorphous Ta2O5 phase or a similar, but not identical, crystalline β-Ta2O5 phase. The Raman spectrum of the material formed at the point of CW laser impingement was in good agreement with the previously established ceramic "H-Ta2O5" phase. TEM and electron diffraction analysis of these particles indicated the phase structure matched an oxygen-vacated superstructure of monoclinic H-Ta2O5. Further from the point of laser impingement, CW heating produced particles with a Raman spectrum that matched β-Ta2O5. We confirmed that the high-temperature ceramic phase characterized in previous work by Raman spectroscopy was the same monoclinic phase characterized in different work by TEM and could be produced by direct laser heating of metal in air.

Enhancing corrosion resistance of lightweight metal alloys through laser shock peening

In this study, we investigated the effects of laser shock peening (LSP) on the corrosion resistance of lightweight metal alloys, specifically AA6061 and AZ31. LSP was performed underwater, using a nanosecond pulse laser and without using a protective coating or layer on the workpiece. The corrosion behaviors of these alloys were analyzed through electrochemical tests, including open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization measurements. The results demonstrated that LSP significantly improved the polarization resistance, and higher laser power intensities led to increased corrosion resistance and reduced corrosion rates. This enhancement in anti-corrosion performance is attributed to the formation of a protective oxide layer on the surface, acting as a barrier against corrosion. The findings underscore the potential of laser surface treatment as a viable technique for enhancing the corrosion resistance of lightweight metal alloys.

Ferroelectricity in Ultrathin HfO2-Based Films by Nanosecond Laser Annealing.

Nonvolatile memory devices based on ferroelectric HfxZr1-xO2 (HZO) show great promise for back-end integrable storage and for neuromorphic accelerators, but their adoption is held back by the inability to scale down the HZO thickness without violating the strict thermal restrictions of the Si CMOS back end of line. In this work, we overcome this challenge and demonstrate the use of nanosecond pulsed laser annealing (NLA) to locally crystallize areas of an ultrathin (3.6 nm) HZO film into the ferroelectric orthorhombic phase. Meanwhile, the heat induced by the pulsed laser is confined to the layers above the Si, allowing for back-end compatible integration. We use a combination of electrical characterization, nanofocused scanning X-ray diffraction (nano-XRD), and synchrotron X-ray photoelectron spectroscopy (SXPS) to gain a comprehensive view of the change in material and interface properties by systematically varying both laser energy and the number of laser pulses on the same sample. We find that NLA can provide remanent polarization up to 2Pr= 11.6 μC/cm2 in 3.6 nm HZO, albeit with a significant wake-up effect. The improved TiN/HZO interface observed by XPS explains why device endurance goes beyond 107 cycles, whereas an identical film processed by rapid thermal processing (RTP) breaks already after 106 cycles. All in all, NLA provides a promising approach to scale down the ferroelectric oxide thickness for emerging HZO ferroelectric devices, which is key for their integration in scaled process nodes.

Preliminary study on temperature distribution and pyroelectric current of LiNbO3 heated by nanosecond pulse laser

In order to reduce the volume of compact neutron generators, a lot of investigations are carried out on generating high voltages by heating pyroelectric crystals with external heating. Laser irradiation is an effective non-contact heating method. Different laser parameters determine the crystal's temperature distribution, impacting the accelerating electric field. A preliminary study on the temperature distribution and pyroelectric current response of LiNbO3 heated by nanosecond pulse laser is presented, including both direct heating and heating with Cu and Ti disks adhered to the crystal. A two-dimensional transient heat transfer and circuit model is constructed in COMSOL. To validate the simulation model of temperature field distribution, FLIR thermal camera is utilized to measure the temperature in laser spot center experimentally. The experimental results coincide with simulations, which prove that the simulation model can predict temperature field distribution of the pyroelectric crystal effectively. This study can benefit the optimization of laser parameters for modulating high-quality deuterium ion acceleration fields.

Experimental Proof of the Effect of Induced Optical Coalescence of Bubston Clusters at Water Breakdown Induced by Picosecond and Nanosecond Laser Pulses

Experimental Proof of the Effect of Induced Optical Coalescence of Bubston Clusters at Water Breakdown Induced by Picosecond and Nanosecond Laser Pulses

A Study on the Manufacture of CNT Composites Bipolar Plate for the Fuel Cell Using a Nanosecond Pulsed Laser

The channels of the graphite-based bipolar plate for hydrogen fuel cells were mainly manufactured through milling due to low forming elongation and processability. However, during the milling process, the machining precision is low due to tool wear and vibration, and there is a risk of breakage. Non-traditional laser processing can solve the problems of tool wear and vibration through non-contact processing. In this study, the interaction characteristics of the nanosecond pulsed laser and CNT composites were observed, and channels and bipolar plates were manufactured. The effect of scanning speed and pulse duration was observed for interaction characteristics. Defects were observed due to high thermal effects at low scanning speed and high pulse duration. Channels were created depending on parallel pitch distance [] and Number of scans (NOS). The channel was evaluated for depth, top width, bottom width, channel angle, material removal rate, and surface roughness, and significant changes were observed depending on . The chemical composition, surface resistance, and contact angle of the laser-processed channel were measured. The laser processed channel was oxidized, and the surface resistance and contact angle increased. Finally, the manufacturability of the CNT composites bipolar plate using laser was examined.

Nanosecond pulsed laser coloring of the CrMnFeCoNi high entropy alloy

High-entropy alloys (HEAs) possess great potential for applications in the aerospace and military fields due to their excellent performance. Surface coloring can endow HEAs diverse functions. However, achieving a multi-color surface with minimal surface damage and cost remains a significant challenge. In this study, surface coloring of the CrMnFeCoNi HEA was attempted by nanosecond pulsed laser irradiation in air, and the multi-color surface was achieved. The evolution of surface color and morphology with laser parameters was analyzed. Then, five typical colors were selected, and the corresponding morphologies and chemical compositions were characterized by various techniques. The results showed that the change in oxide layer thickness as well as the formation of chromium-rich β-spinel and Cr (VI) compounds induced noticeable changes in surface color. Accordingly, complex surface patterns with various stable colors were prepared on the HEA surface, demonstrating the potential application of nanosecond pulsed laser coloring of HEAs.

The spatio-temporal evolution of shock wave pressure induced by laser: Effects of laser parameters and confinement layer

The spatio-temporal distribution of the shock wave pressure on the surface of the target is the key to the performance of laser shock processing (LSP), which is mainly determined by the laser parameters and the confinement layer. The two-dimensional kinetic simulations of the expansion process of the shock wave induced by irradiation of an aluminum target with nanosecond laser pulses are performed. It is found that by controlling the gap between the rigid confinement layer and the aluminum target, and the interval time between the double pulse laser pulses, multiple peaks appear on the shock wave pressure-time curve of the aluminum target surface, and the value and interval time of each peak will change.

Extending mid-infrared wavelength to 6.84 μm in oxide nonlinear optical crystal via birefringence dispersion management.

Extending lasing wavelengths to the mid-infrared (MIR) spectrum is vital for both civilian and military applications; however, it remains challenging when employing oxide nonlinear optical crystals. In this study, we report the generation of MIR nanosecond pulses via difference frequency generation (DFG) with a near-IR pump using a newly designed langasite (LGS) crystal, La3(Nb0.6Ta0.4)0.5Ga5.5O14 (LGNT0.4), which incorporates birefringence dispersion management techniques with La3Ga5.5Nb0.5O14 (LGN) as a template. Due to the improved effective nonlinear coefficients and the maintained IR cutoff relative to LGN, the tunable DFG laser in LGNT0.4 extended from 4.24 to 6.84 μm, delivering a maximum pulse energy of 16.3 μJ at 5.02 μm. To the best of our knowledge, this is the first known oxide material capable of generating tunable nanosecond pulsed lasers beyond 6 μm at μJ-level energies, demonstrating promising potential for high-intensity MIR laser systems owing to its high laser damage threshold.

Nickel oxide nanoparticles embedded in polymer-matrix nanocomposite prepared by nanosecond laser ablation method for optoelectronic applications

The polymeric PVA structure embedded with nickel oxide nanoparticles (NiO NPs) was synthesized using nanosecond pulsed laser ablation in liquid media technique for optoelectronic applications. A comprehensive investigation was conducted on the optical and electrical characteristics of the fabricated films to demonstrate the proficiency of the proposed nanocomposite film in that particular domain. Different weights of NiO nanoparticles were generated by embedding them in PVA film using different ablation durations. It was shown that as the concentration of NiO embedded in PVA increased in correlation with the ablation period, the absorption peak changed to a longer wavelength, and the absorption edge of PVA changed towards lower photon energy with a reduction in the band gap density. Followed by the increase in disorder degree through the addition of NiO NPs, while an average value of the dispersion energy is identical, and the nonlinear parameters (χ(3) and n2) increase. Also, the results emphsies that the dielectric characteristics were affected as the concentration of NiO NPs increased due to the rise in the density of states, which resulted in the generation of polarization. Due to the creation of the charge transfer complex, the optical conductivity of the produced nanocomposites rises as the concentration of NiO NPs increases. Therefore, the optical and electrical characteristics of PVA are significantly affected by the incorporation of NiO nanocomposites.

Ultra-Fast Synthesis of Highly Dispersed Pt Nanoclusters Anchored on Sulfur-Doped Porous Carbon Carriers by Nanosecond Pulsed Laser for Hydrogen Evolution Reaction.

Nanosecond pulsed laser irradiation is employed for synthesis of highly active and stable Pt-based electrocatalysts by anchoring Pt nanoclusters on porous sulfur-doped carbon supports (L-Pt/SC). Strong metal-support interaction (SMSI) between Pt and S induces a local charge rearrangement and modulates the electronic structure of Pt surroundings, thus boosting the reaction kinetics and enhancing stability in long-term hydrogen evolution reaction (HER). The L-Pt/SC catalyst exhibits high activity toward HER, with an overpotential of 23 mV at current densities reaching 10 mA cm-2 and a Tafel slope of 24mV dec-1. The unit mass activity of L-Pt/SC is calculated to be -10.8 A cm-2 mgPt -1 at an applied voltage of -0.3V versus RHE. In situ Raman spectra reveals that L-Pt/SC catalyst exhibits fast hydrogen production efficiency and its electrocatalytic HER process is determined by the Tafel step. Density functional theory calculations suggest the strong bonding energy between SC and Pt induces the formation of smaller nanoclusters of L-Pt/SC during fast pulsed laser preparation, which increases the effective contact area during the HER process thereby increasing the activity per unit mass.

An interior damage free approach for nanosecond pulsed laser ablation of single crystal diamond via metal film induced self-maintaining graphitization

When laser ablation was conducted on an uncoated single-crystal diamond (SCD) substrate, interior damage and random ablation were observed. Metal film-induced self-maintaining graphitization (MISG) was proposed as a generic approach to solve this problem. MISG was realized through coating a ∼ 100-nm-thick metal film on an SCD substrate. Experiments involving laser irradiation of metal films, such as Au-, Al-, Ti-, and Pt-coated SCD substrates, revealed that the material removal depths were the same when the output power was the same and that the surface was covered by graphite after laser irradiation. In addition, the laser-induced damage to the upper or lower surface in the case of the uncoated SCD substrate disappeared. A semitransparent model based on Beer-Lambert law and an opaque model based on modified Level-Set method were built to simulate laser irradiation on uncoated and metal–coated SCD substrates. In the case of the uncoated sample, the laser energy was largely absorbed by the areas with high-concentration defects, leading to preferential graphitization. In the case of the metal-coated sample, a graphite layer was thermally induced on the SCD surface via heat transition during the period of laser irradiation of the metal film. Subsequently, the graphite layer was self-maintaining, and the material removal acted like a graphite piston sinking to the interior of the SCD substrate. This study demonstrates the feasibility of MISG as a universal approach for avoiding interior damage during laser ablation of SCD substrates.